Research Summaries
Research Summaries
For the three Research Summaries passages, you will have to read and understand two or three experiments and their results. The questions accompanying Research Summaries will ask you to compare data across the experiments.
The Sample Passage
Brine shrimp, also called artemia, are tiny arthropods that are often used as live food in aquariums. The shrimp begin their life cycle as metabolically inactive cysts. The cysts can remain dormant for many years if they remain dry. If these cysts come in contact with salt water, they soon rehydrate and hatch, giving rise to living embryos.
Experiment 1
Scientists placed dormant brine shrimp cysts into three different soda bottles containing salt water. The scientists maintained the water in each container at a constant temperature of 25º Celsius (77º Fahrenheit), but they kept the salt concentration (milligrams of NaCl per liter of ) of each bottle at different levels. The scientists then recorded the average hatching rate for the cysts in each bottle.
Temperature (˚C) Salt Concentration (mg/L) Average Time to Hatching (hours)
Bottle 1 25 0.2 20
Bottle 2 25 0.3 17
Bottle 3 25 0.4 15
Experiment 2
The scientists repeated Experiment 1, except in this experiment they kept the salt concentration constant while changing the temperature in each bottle.
Temperature (˚C) Salt Concentration (mg/L) Average Time to Hatching (hours)
Bottle 1 15 0.3 33
Bottle 2 25 0.3 17
Bottle 3 35 0.3 26
Experiment 3
The scientists repeated Experiment 1, but placed all three bottles in the dark. The chart below shows the average hatching rate (in hours) for the brine shrimp in the three bottles in Experiment 1 and Experiment 3.
Experiment 1 Experiment 3
Bottle 1 20 35
Bottle 2 17 28
Bottle 3 15 25
Strategy for Reading the Passage
Earlier, we advised you to take notes while reading the passage. Marginal notes and underlines will particularly help you in reading the Research Summaries passages, which each present you with two or three sets of data.
No matter how carefully you read, you should refer back to the passage when answering the questions. However, if you read too quickly the first time, you run the risk of misunderstanding the basic premise of a passage, and you’ll waste time trying to sort out the information when you should be answering the questions.
For this particular passage, jotting down the variables in each experiment in the margins of the passage will help you recall the differences between the experiments. For instance, you might want to write “hatching time” at the top of the passage, so you’ll remember that all three experiments test the effect of variables on the hatching time of brine shrimp. Next to Experiment 1, you can write something like “salt conc” to indicate that salt concentration was varied in that experiment. Next to Experiment 2, scribble “temp” to indicate that temperature was the variable. Write “light” or “light vs. dark” next to Experiment 3 to show that the experiment tested hatching time with and without light.
The Questions
Each Research Summaries passage will be followed by six questions. These questions will be similar in type to the questions on the Data Representation passages. All of the questions in this section refer to the sample Research Summaries passage above.
Read the Chart
As on the Data Representation passage, the Read the Chart questions will ask you to identify information that is explicitly stated in a chart in the passage. For example,
Based on the results from Experiment 1, one can conclude that:
A. brine shrimp hatch less quickly as salt concentration increases.
B. brine shrimp hatch more quickly as salt concentration increases.
C. hatching is unaffected by salt concentration.
D. salt concentration is dependent on temperature.
Since three of the answer choices deal with the hatching of brine shrimp, you should probably look at the column “Average Time to Hatching” and see how the numbers in it change. By reading the chart, you can see that a 0.2 salt concentration corresponds with 20 hours to hatching, a 0.3 salt concentration corresponds with 17 hours to hatching, and a 0.4 salt concentration corresponds with 15 hours to hatching; thus hatching time decreases as salt concentration increases, or brine shrimp hatch more quickly as salt concentration increases. Choice B seems to be the correct answer. Still, it’s good policy to make sure that choices C and D do not work before committing to your answer. You can easily eliminate choice C, which states that salt concentration has no effect on hatching time, because Experiment 1 demonstrates the effect of salt concentration on hatching time. Similarly, you can eliminate choice D because it claims that salt concentration depends on temperature. From the chart, you can see that temperature did not vary in Experiment 1, so salt concentration, which did vary, could not have been dependent on it. You’ve already eliminated choice A by concluding that shrimp hatch more quickly as salt concentration increases, so that leaves you with the correct answer, which is B.
Here’s another Read the Chart question:
Which of the following was studied in Experiment 3?
A. The effect of light on the time it takes for brine shrimp to hatch.
B. The effect of light on salt concentration.
C. The effect of light on temperature.
D. The effect of light on the survival rate of brine shrimp.
This question asks you about Experiment 3, and all four answer choices deal with the effect of light on an aspect of the experiment. Your job is to figure out which aspect of the experiment light affects. A quick look at your marginal notes will reveal that Experiment 3 deals with the hatching time of brine shrimp in the dark, using Experiment 1 as a control. You can either look to the chart or its written introduction to find the answer to this question. If you read the introduction, it tells you that the following chart shows the average hatching rate of brine shrimp under the altered circumstances. The chart presents you with no other information, so the experiment must be testing the effect of light on the hatching time of brine shrimp, or choice A.
Use the Chart
Use the Chart questions accompanying Research Summaries passages are very similar to the ones accompanying Data Representation passages. For example,
If the standard salt concentration used in Experiment 2 were changed from 0.3 mg/L to 0.4 mg/L, what would likely happen to the time it takes for the cysts to hatch?
F. The time would increase.
G. The time would decrease.
H. The time would not change.
J. The time would be reduced to zero.
Answering this question requires that you use the charts for both Experiments 1 and 2. As usual, you should see whether you can eliminate one of the answer choices right off the bat. Choice J seems like a prime candidate for elimination because neither experiment indicates that the brine shrimp will hatch immediately under any circumstances. To figure out the most likely hatching time, you should look at Experiment 1, which tests changes in salt concentration. The question asks you what would happen if the salt concentration were raised from 0.3 mg/L to 0.4 mg/L. Luckily for you, Experiment 1 tells you what happens to the hatching rate at 0.4 mg/L concentration and 25º temperature: the brine shrimp take 15 hours to hatch. Compare this to the 17 hours it takes for brine shrimp to hatch at 0.3 mg/L and 25º, and you can predict that hatching time will decrease with increased salt concentration. So the best answer for this question is G.
Here’s a more difficult Use the Chart question:
Under which of the following conditions would you expect a brine shrimp cyst to hatch in the least amount of time?
A. In the light, in water with 0.2 mg/L salt concentration at 25 degrees Celsius.
B. In the dark, in water with 0.3 mg/L salt concentration at 35 degrees Celsius.
C. In the light, in water with 0.4 mg/L salt concentration at 25 degrees Celsius.
D. In the dark, in water with 0.2 mg/L salt concentration at 25 degrees Celsius.
This question requires that you use all three charts and a little intuition. Some of the answer choices are lifted directly from information in the charts. Choice A, for instance, represents Bottle 1 in Experiment 1, with a hatching time of 20 hours. Choice C, or Bottle 3 in Experiment 1, has a hatching time of 15 hours. Choice D, Bottle 1 in Experiment 3, has a hatching time of 35 hours. Choice B is a little trickier than the other answer choices because you must make an educated guess as to its hatching time. The choice states that the bottle is in the dark, so you should keep Experiment 3 in mind. It also states that it has a 0.3 salt concentration and 35˚ temperature. Since Experiment 1 keeps the temperature constant at 25˚, you need to look to Experiment 2, which maintains a 0.3 salt concentration but varies the temperature among 15˚, 25˚, and 35˚. The hatching time for Bottle 3 in Experiment 2, which has the same temperature and salt concentration as choice B, is 26 hours. Since the dark only increases the hatching time for brine shrimp, you can guess that it will take choice B much more than 26 hours to hatch. To keep track of all these hatching times, write down the number of hours for hatching next to each answer choice. The last step in answering the questions should be to compare these numbers and choose the smallest one. The correct answer is C, with a hatching time of only 15 hours.
Handle Graphs
Questions that ask you to handle graphs on the Research Summaries passage will ask you to transfer information from verbal to graphic form or the other way around. For example:
Which of the following graphs best represents the change in hatching time with increasing temperature as shown in Experiment 2?
F.
G.
H.
J.
From the data given with Experiment 2, you can tell that hatching time goes from high to low to high again as temperature increases. These graphs show temperature on the x-axis, or horizontal axis, so as you move to the right along the horizontal axis, you are increasing temperature. Similarly, as you move up the y-axis, or vertical axis, which represents hatching time, you are increasing the hatching time—33 hours will be higher up on the y-axis than 17 hours. Putting all this information together, you should be able to figure out that choice J is correct. If you want proof, you can eliminate the other choices: choice F shows a steadily increasing hatching time; choice H shows a hatching time that doesn’t change; and choice G shows a hatching time that goes from small to big to small again, the opposite of what occurs in Experiment 2 Again, review the graphic representations of linear and exponential functions if you are unfamiliar with them.
Take the Next Step
These questions will be exactly like the Take the Next Step questions on the Data Representation passages. The question will provide you with a new research goal, and you must decide how to achieve it. For example,
What would be the best way to study the effects of changing pH (acidity) on the hatching time of brine shrimp cysts?
A. Putting all three bottles in the light and keeping temperature constant while changing salt concentration and pH.
B. Putting all three bottles in the dark and keeping temperature constant while changing salt concentration and pH.
C. Putting all three bottles in the light and keeping temperature and salt concentration levels constant while varying the pH in each bottle.
D. Putting all three bottles in the dark and varying temperature, salt concentration, and pH in all three bottles.
This question asks you to make pH the variable in the new experiment. Since pH is the variable in this new experiment, you want to keep the other factors as constant and as “normal” as possible. But choices A, B, and D all ask you to change other factors, such as salt concentration or temperature. These modifications would make it tough to tell whether a change in hatching time was caused by a change in pH levels or by one of the other variables, and that defeats the goal of the experiment. C, the only choice that keeps light, salt concentration, and temperature constant, is the correct answer.
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